Balanced single passage impeller pump



Sept. 23, 1958 R. s. THORNTON 2,853,019

BALANCED SINGLE PASSAGE IMPELLER PUMP f Filed Sept. 1. 1954 5Sheets-Sheet 1 ATTORNEYS Sept. 23, 1958 R. S. THORNTON BALANCED SINGLEPASSAGE IMPELLER PUMP Filed Sept. 1. 1954 5 Sheets-Sheet 2 Fic-sBINVENTOR zs Richard. S.Thqrn'ton ATTORNEYS Sept. 23, 1958 R. s. THCRNTON,0

BALANCED SINGLE PASSAGE IMPELLER PUMP 5 Sheets-Sheet 4 Filed Sept. 1.1954 INVENTOR Rxchard sTl'lolr'rflron ATTORNEYS Sept. 23, 1958 R. s.THORNTON BALANCED SINGLE PASSAGE IMPELLER PUMP 5 Sheets-Sheet 5 FiledSept. 1, 1954 R 0 mn 0 v}. n r O h T S d r m .m R a 7 2 a /16 2 BY bnzin A.

ATTORNEYS Patented Sept. 23, 1958 2,353,019 EALANCEDSINGLE PASSAGEIMPELLER PUMP Richard S. Thornton, Aurora, 111;, assignor to- The NewYork Air Brake Company, a corporation of New Jersey ApplicationSeptember 1, 1954, Serial No. 453,479

7 Claims. (Cl; 103103) This invention relates to non-cloggingcentrifugal pumps.

The commercial art became active about forty years ago, with the workof'Albert B. Wood; Patent 1,182,439, and continued for many years on thebasis of twin passage impellers in a snail-shell housing. These have theadvantage of inherent balance but do clog on stringy material. The artapparently overlooked the single passage impeller of the Seitz Patent495,760, perhaps be cause 1893 too long preceded the demand for sewagepumps. Another possibility is that the Seitz design was tried and foundunsatisfactory. A single passage impeller' is not inherently balanced.It develops. hydraulic forces that vary with. operating. conditions and.tend to defeat balance. Seitz discloses nothing as to balance exceptpossibly static balance which is a. small factor in the problem.

As a practical matter non-clog single-eye'impellers must be mounted onthe end of a rotary shaft. in overhung relation to the shaft bearings.In such case radial forces which cause faulty running-balance leadquicklyto shaft breakage.

Attempts to balance single passage impellers have been: made withpalliative effects, but past methods depended on the use of unchangingbalancing masses. Hence prior art balanced impellers cannot meet thechanging conditions inherent in the service. only in limited ranges.

Static balance is never the sole determining. factor. Running-balance isaffected by changing factors. The mass of the impeller rotor is a fixedquantity, but the mass of the flowing stream varies with the nature ofthe liquid being pumped. Worse still, are those varying unbalancingforce reactions developed by the flowing liquid between the rotatingimpeller and the enclosing housing. These forces are large and they varywith, speed of rotation, discharge head and thespecific weight of. theliquid being pumped.

The invention provides a rotary impeller in which the impeller carriesunpumped free liquid whose mass. and. motion closely approximate themass and motion of. the pumped liquid, but whose balance destroyingtendency is 180 out of phase with that of the pumped liquid. To producethis effect the impeller carries peripherally exposed sockets similar inform to the single pumping passage, arranged to fill with liquid passingthrough the pump, and diametrically opposed on the impeller to thepumping passage.

Then, if the impeller is designed to be in running balance in air, itwill run in balance when pumping, or nearly so. Obviously rotary flowingliquid passing through the pumping volute, and liquid short-circuited inthe balancing passages and reflux chambers, develop somewhat differentforces so that. true perfection is not attainable, but it is approachedto an extent hitherto not considered possible. The results arecommercially satisfactory and better than can be had with any fixed'massbalancing scheme. Obviously axial forces should be They are successful2?. balanced, but the invention impos'es'no penalty in this; respect.

The drawings show the invention incorporated in 3L centrifugal pumphaving a vertical shaft axis; It is adaptable'to pumps having horizontalaxes. In fact the position of the shaft axis is a matterof choice.

Fig. 1 is a fragmentary view showingtheimpeller and the enclosinghousing chiefly in axial section and on a reduced scale.

Fig. 2 is a simplified horizontal section on the line2-2 of Fig. 1intendedto show the snail-shell contour ofthe housing.

Figs. 3 to 8 are views of the impeller drawn toa somewhat larger scalethan Fig; 1.

Fig. 3 is a plan view.

Fig; 4 is a front elevation of the impeller positioned as in Fig. 3.

Fig. 5 is a section on the line55'ofFig; 4.

Fig. 6 is an elevation looking'in the direction of the arrow 6'in Figs.3 and 5.

Fig. 7 is a bottom view, i. e. a view looking into the" eyeof theimpeller.

Fig. 8 is a section on theline-88 of Fig. 7.

Fig. 9 is a view similar to Fig. 5 showing a modification.

Fig. 10 is a view similar to Fig. 8 showing another modification.

Statements of direction refer to parts positioned as" in Fig. 1.

The housing of the pump comprises a volute or snailshell member 11 ofknown form with discharge passage 12. See Figs; 1 and 2. The member 11is annular in form but closed at the bottom by plate 13 with centralinlet passage 14 and at the top by plate 15 with a central opening forthe impeller shaft 16; The cylindrical flanged member 17 encloses andsupports some driving unit for shaft 16, customarily an electric motor(not shown).

As clearly shown in the drawing the parts' 11 and 13" are connected bystuds. So also are the parts 11, 15' and the flange on member 17..Gaskets, also shown in the drawing, sealthe members 13 and 15 to member11.

The impeller, indicated generally by the numeral 18 is cylindrical inexternal outline and includes an external hub 19 keyed to shaft 16 andclamped against a journal sleeve 21 on shaft 16'by the machine screw 22and washer 23. The sleeve 21 turns in a packing or sealing unitconventionally represented at 24.

Thehub 19 projects from the upper side of the impeller 18, and from thelower side projects a neck'25which' has a terminal plane surface 26-(normal to the axis of shaft 16). Surface 26 makes a free running fitwith the plane upper face of member 14 around the eye 27 of'theimpeller. Eye 27 registers with passage-14, said" eye and passage beingcoaxial with shaft 16. The neck'25 is not symmetrical with respect to'the impeller axis, a portion of it being reduced in thickness behind aflange 28, for reasons which will be discussedhereinafter.

Reference should now be made to Figs. 3-8 which show the impeller on alarger scale and in greater detail. The section in Fig. 8 corresponds tothat in Fig. 1.

As best shown in Figs. 5 and 8 the eye 27 communicates with a volutepassage 29. This can be dimensioned to pass any solid which will enterthrough the eye, according dimensionradial to the impeller 18) butthroughout'this am. it is open to the volute housing 11. The channellies between flanges 33, 34 which continue the circular contour of theimpeller.

The passage 29 is a Void within the impeller, and to balance this, useis made of two voids of approximately equal aggregate volume andsubstantially identical volute contour, both displaced from passage 29by an arc of 180 measured about the periphery of the impeller,

These voids are identified by the numerals 35 and 36 (see particularlyFigs. 3 and 7) and are separated by a web 37 (see Figs. 4, 6 and 8)whose periphery continues the circular contour of the impeller. While,as above stated the design of volute passage 29 can be varied accordingto principles known in the art, it is important that the voids 35, 36 besimilar in volute contour to passage 29 and of basically equal aggregatecross section therewith.

Channel 35 starts at 38 adjacent hub 19 (see Fig. 3) and 36 starts atthe similar point 39 behind the flange 28. Indeed the flange is used topermit the necessary undercut. The channels start to emerge on theperiphery of the runner at 40 diametrically opposite 31 and terminate at41 diametrically opposite 32. The Web 37 is of such thickness and sofilleted as to match the mass of the shrouding flanges 33 and 34, which,be it noted are similarly filleted. The thickness of web 37 is desirablyheld to a minimum where the web commences at 38, 39, i. e. opposite theopening from eye 27 into passage 29. This favors balance. The extrametal shown at 42 has a similar balancing function.

The spaces 43 and 44 which are clearly shown in Fig. 1, are importantfactors as to balance of the impeller. When the pump is running thesespaces are liquid-filled and the liquid is that which is being pumped.In its dry condition, the impeller is in static balance andapproximately running balance so its effect on balance is negligible.When the pump is in operation liquid flows continuously through passage29. There is also recirculatory flow from each of the spaces 43 and 44outward through the corresponding passages 35 and 36 and back to thespaces 43 or 44 as the case may be. While the hydraulic reactions do notprecisely match, they are basically similar and the effect is a closeapproximation to hydraulic balance.

Impellers designed to handle solids of very large size present increaseddifiiculty as to static and dynamic balance because the arc subtended bythe junction of eye 27 and passage 29 is large. In such case recoursemay be had to the modified construction of Fig. 9. In this figure partsidentical with those in Fig. 5 are identically numbered. Themodification is the presence of an opening 45 through the web 37 in thesector opposite the junction of eye 27 and passage 29. In eifect the webin this area is made so thin that it actually or substantiallydisappears. The static and dynamic balancing effects diife'r only indegree from those secured with the construction of Figs. 1-8, for thelocation of the area 45 conforms substantially to the area in which theweb is made as thin as practicable in the embodiment of Figs. 1 to 8.

An opening through the web is not considered desirable because it mightlead to clogging. It could be used in the case of rotors which for somereason present an extreme balancing problem.

The impellers shown in Figs. 1-8 and 9 have the web 37 centered in theperiphery of the impeller. In the absence of special considerations,this is deemed to be the best arrangement, but it is not the onlypracticable arrangement within the broad scope of the invention. Fig. 10shows a limiting case in which the Web 37a is along one edge of theperiphery of the impeller. Parts in this view corresponding to partsshown in Fig. 8 are numbered as in Fig. 8 with the distinguishing lettera.

The arrangement shown in Fig. 10 avails of only one of the refluxchambers 43 or 44, and hydraulic forces developed in the direction ofthe axis of rotation do not neutralize each other to the extent thatthey do in the structures of Figs. 18 and 9. However, the arrangement isworkable and may even be desirable in cases where it can be used tobalance out axial thrusts exerted on the shaft by the weight of theparts or other factors.

Prototypes have been built and tested in practical service, and havedemonstrated good pumping performance, ability to pass stringy materialwithout clogging, and remarkable freedom from vibration, not merely atone speed, but over as wide a range as is likely to be encountered incommercial use.

The invention provides a single passage impeller which has not only goodrunning balance as to its own mass, but also good running balance as toliquid which fills it, and above all good running balance as to thehydraulic forces which its operation necessarily develops between theimpeller and the housing. Attainment of the third effect affords abilityto operate successfully over a wide performance range.

I claim:

1. In a centrifugal pump, the combination of an enclosing housing havingan annular channel and a discharge passage leading therefrom; agenerally cylindrical impeller encircled by said channel and spaced fromsaid housing to afford a reflux space comprising at least one annularreflux chamber, said impeller having a single eye coaxial with theimpeller, and at least two volute passages of substantially identicalvolute profiles displaced from each other by of arc measured on thecircumference of the impeller, one of which volute passages communicatesat its inner end with said eye and at its outer end with said annularchannel and another of which volute passages is closed from said eye atits inner end and is in communication with said reflux space; meansdefining an inlet passage leading to said eye; and means for rotatingsaid impeller about its geometric axis.

2. In a centrifugal pump, the combination of an enclosing housing havingan annular channel and a discharge passage leading therefrom; agenerally cylindrical impeller encircled by said channel and spaced fromsaid housing to afford two reflux chambers, said impeller.

having a single eye coaxial with the impeller, and volute passages ofsubstantially identical profile, the first of which communicates withthe eye, and the two others of which are closed from the eye, are ofaggregate cross sectional area equal to the cross sectional area of thefirst passage and displaced 180 of are from the first passage asmeasured around the impeller, said first passage merging into theperiphery of the impeller between shrouding flanges, and the other twobeing separated by a web whose cross section matches the aggregate crosssection of said flanges; means defining an inlet passage leading to saideye and means for rotating said impeller about its geometrical axis.

3. The combination defined in claim 2 in which said web substantiallybisects the periphery of the impeller so that the passages separatedthereby are equal in cross section throughout their lengths.

4. The combination defined in claim 2 in which the passage whichcommunicates with the eye is substantially uniform in cross section fromthe eye to its point of merging with the periphery of the runner.

5. The combination defined in claim 2 in which, within a sector oppositethe junction of the eye with said volute passage, said web diminishes inthickness substantially to zero in an area outside, but closelyadjacent, said eye.

6. The combination defined in claim 2 in which said web substantiallybisects the periphery of the impeller so that the passages separatedthereby are equal in cross section throughout their lengths, and withina sector opposite the junction of the eye with said volute passage, saidweb diminishes in thickness substantially to zero in an area outside,but closely adjacent, said eye.

7. In a centrifugal pump, the combination of an enclosing housing havingan annular channel and a discharge passage leading therefrom; agenerally cylindrical impeller encircled by said channel and spaced fromsaid housing to afford a single reflux chamber, said impeller having asingle eye coaxial with the impeller and tWo volute passages ofsubstantially identical volute profiles displaced from each other by 180of are measured on the circumference of the impeller, one of whichvolute passages communicates at its inner end With said eye and at itsouter end with said annular channel, and the other of which volutepassages is closed from said eye at its inner end and is incommunication with said reflux space throughout a major portion of itslength; means defining an inlet passage leading to said eye; and meansfor rotating said impeller about its geometrical axis.

UNITED STATES PATENTS Perry Jan. 15, Samelson Mar. 30, Wood Jan. 3,Schellens Jan. 25,

FOREIGN PATENTS Germany Feb. 18, Great Britain Mar. 20, Great BritainDec. 19, Germany Apr. 20, Germany Dec. 20,

